This invention relates to superchargers for internal combustion engines and more particularly to centrifugal superchargers of the type which are mechanically driven by the associated engine.
Supercharging of internal combustion engines is a well established method of obtaining greater power output from engines of a given size. In recent years because of problems with both availability and price of gasoline, engines have been made smaller to improve mileage. Some of the larger engines have been retained, especially for truck use, but have been derated as to horsepower. These measures have improved fuel mileage but performance has often been unsatisfactory.
The turbo-supercharger or turbocharger has become a popular option for getting greater power engines of all sizes, especially relatively small engines. While this is an effective means of getting greater horsepower out, there are some problems with this type of supercharger. Turbochargers, because they are exhaust driven, tend to raise temperatures in both the engine and engine compartment. Because of such heat, they also require special, more expensive materials not required by mechanically driven superchargers. Typically, oil change intervals are shorter than when no turbo-charger is installed; the high speed of the exhaust driven turbine which runs on bearings lubricated by the engine oil requires a certain amount of time to decelerate; consequently, the engine cannot or should not be stopped immediately since this may result in starving the turbine bearings (which run very hot) for oil over a significant time period. This can result in frequent replacement of those bearings. Since the engine exhaust flow drives the turbine, there is little such flow available at low speeds, consequently there is little power boost at low engine speeds. An additional disadvantage is that there is often a significant lag between the time the additional power is requested through depressing the accelerator pedal and the delivery of such power.
Because of the above problems there has been increased in interest in the type of supercharger which is driven directly by the engine through a mechanical link. Such superchargers have been available for decades but have enjoyed limited success because of susceptibility to wear, because of expense of installation, and at least partly because of limited space in the engine room. Further, since most engines are designed for forces resulting from normal aspiration, there is a concern about imposing additional bearing loads and other stresses from supercharging.
Although there has been a substantial amount of development work on turbochargers, no comparable amount of development effort has been expended on mechanically driven superchargers. This is at least partially due to the fact that, until very recently, no major auto manufacturer has been willing to fund the development expense to 1) develop a good system and 2) to adapt such a supercharger to several different models. Applicant has been aware of the above shortcomings of such superchargers and has recognized a need to provide a supercharger using current technology which o avoids most of the above disadvantages. There is a need for a supercharger which is durable, efficient, and readily installed on engines of different types.